Hmmmmm,
O.K.
I flagged the ones I want gone and clicked "Leave conversation".
Then selected "Ignore future messages".
Then said "Yes".
Messages disappeared from the list, but are they still being stored ???
My point is that if they are STILL being stored, eventually that stored space will grow and grow and grow...........
Think a faucet dripping into a sink...
One drip at a time....
Over an hour not much water in the sink...
Over a week a LOT more water in the sink...
At some later time enough water will be in the sink that it will overfill onto the floor.....